Question

A disc rotates about its axis of symmetry in a horizontal plane at a steady rate of
3.5 revolutions per second. A coin placed at a distance of 1.25 cm from the axis of
rotation remains at rest on the disc. The coefficient of friction between the coin and
the disc is $\left( g=10m/{{s}^{2}} \right)$
A. 0.5
B. 0.7
C. 0.3
D. 0.6

Answer 1

Hint: A coefficient of friction is a worth that shows the connection between two objects and the typical response between the objects that are included.

Complete answer:
It is a worth that is some of the time utilized in material science to discover an object's typical force or frictional force when different strategies are inaccessible.
The correct answer is D.
$3.5rev/second$
$1rev\to 2\pi rad$
$3.5rev\to 2\pi \times 3.5rad$
$\Rightarrow w=7\pi rad/\sec$
$\mu mg=\dfrac{m{{v}^{2}}}{1.25}$
$\mu mg=\dfrac{m{{(r\omega )}^{2}}}{r}$
$\mu mg=mr{{\omega }^{2}}$
$\mu =\dfrac{r{{\omega }^{2}}}{g}=\dfrac{1.25\times {{10}^{-2}}\times {{\left( 7\times \dfrac{22}{7} \right)}^{2}}}{10}$
$\dfrac{1.25\times {{10}^{-2}}\times {{22}^{2}}}{10}$
$=0.6$
The coefficient of friction has no dimension and it doesn't have any unit. It is a scalar, which means the course of the force doesn't influence the physical amount.
The coefficient of friction relies upon the objects that are causing friction. The worth is for the most part somewhere in the range of 0 and 1 yet can be more prominent than 1. An estimation of 0 methods there is no friction at all between the objects; such is conceivable with Superfluidity. All objects, in any case, will have some friction when they contact one another.
An estimation of 1 method the frictional force is equivalent to the typical force. It is a misguided judgment that the coefficient of friction is restricted to values somewhere in the range of zero and one.
If coefficient of friction that is more than one just implies that the frictional force is more grounded than the typical force. An object, for example, silicone elastic, for instance, can have a coefficient of friction a lot more noteworthy than one.

Note: The friction force is the force applied by a surface when an object moves across it - or puts forth an attempt to move across it.
The coefficient of friction has various qualities for static friction and kinetic friction. In static friction, the frictional force opposes force that is applied to an object, and the object stays very still until the force of static friction is survived. In kinetic friction, the frictional force opposes the motion of an object.
For the instance of a block sliding on a clean wooden table, the coefficient of kinetic friction is about 0.5, which suggests that a force equivalent to half the heaviness of the blocks is required just to defeat friction in keeping the blocks moving along at a consistent speed, and the coefficient of static friction is about 0.6. The frictional force itself is coordinated oppositely to the motion of the object.